Blattodea

Blattodea is an order of insects that contains cockroaches and termites. Formerly, the termites were considered a separate order, Isoptera, but genetic and molecular evidence suggests an intimate relationship with the cockroaches, both cockroaches and termites having evolved from a common ancestor. The Blattodea and the mantises (order Mantodea) are now all considered part of the superorder Dictyoptera. Blattodea includes approximately 4,400 species of cockroach in almost 500 genera, and about 3,000 species of termite in around 300 genera. Termites are pale-coloured, soft-bodied eusocial insects that live in colonies, whereas cockroaches are darker-coloured (often brown), sclerotized, segmented insects. Within the colony, termites have a caste system, with a pair of mature reproductives, the king and the queen, and a large number of sterile workers and soldiers. The cockroaches are not colonial but do have a tendency to aggregate and may be considered pre-social, as all adults are capable of breeding. Other similarities between the two groups include various social behaviours, trail following, kin recognition and methods of communication. Cladistic analysis of five DNA sequences in 107 species representing all the termite subfamilies, all six cockroach families, including 22 of the 29 subfamilies, and 5 of the 15 mantis families (as out-groups) showed that the termites are nested within the cockroaches, and that the Cryptocercidae is a sister group to the termites. The mantids were shown to be the sister group to Blattodea. Cryptocercus also shares characteristics such as species of gut bacteria with the termites. The cockroach families Lamproblattidae and Tryonicidae are not shown but are placed within the superfamily Blattoidea. The cockroach families Corydiidae and Ectobiidae were previously known as the Polyphagidae and Blattellidae. The evolutionary relationships of the Blattodea (cockroaches and termites), based on Eggleton, Beccaloni & Inward (2007), are shown in the cladogram: Over 4000 species of cockroaches are found in every corner of the globe with each continent having its own indigenous species. Most of these are omnivores or detritivores and live in a range of habitats such as among leaf litter, in rotting wood, in thick vegetation, in crevices, in cavities beneath bark, under logs and among debris. Some are arboreal, some live in caves and some are aquatic. A small number of species have taken to living in close proximity to humans in buildings, have been transported around the world by them, and are regarded as pests. Although some species harbour symbionts in their guts which facilitate cellulose digestion, many species also produce enzymes to digest cellulose independent of the symbionts. Over 3000 species of termite are found in all the continents except Antarctica. The greatest diversity is found in Africa and relatively few species inhabit Europe and North America. They are also detrivores and many species eat wood, having specialised guts with symbiotic protozoa to digest the cellulose. Termites have soft bodies and keep out of sight as far as possible. They can loosely be subdivided into dampwood, drywood and subterranean types. In general, dampwood termites inhabit coniferous forests, drywood termites inhabit hardwood forests and subterranean termites live in a wide variety of habitats. Termites are eusocial insects that live in colonies. They operate a caste system, there being a king and queen in each colony and a large number of non-reproductive workers. The workers forage for food which they bring back to the colony to feed the reproductives and the developing young. Cockroaches are also social insects but do not live in colonies, and all adults are able to reproduce. Some species form aggregations, others show an inclination to aggregate, and some exhibit parental care of their offspring.